WASHINGTON (Reuters) - Facing a Wednesday deadline, President Bush has decided to impose tariffs of up to 30 percent on steel imports to help the financially struggling U.S. steel industry rebuild, The Washington Post reported on Tuesday.

The newspaper, citing unnamed administration officials, said the plan Bush endorsed at an Oval Office meeting with advisers would exempt steel imported from Mexico and Canada and several developing nations, including Argentina.

U.S. steel firms and steelworkers have asked for a 40 percent across-the-board tariff for four years on a broad range of steel imports. They blame low-priced imports for 31 bankruptcies since 1997 and are seeking temporary ``safeguard'' protection under ``Section 201'' of U.S. trade law.

The Post quoted steel industry executives as saying the exemptions of countries and products envisioned by the White House could apply to more than one-third of current steel imports, reducing the effectiveness of a tariff plan aimed at the price of U.S.-made steel.

``It's not what we wanted, but we're getting closer to something we can at least say is workable and helpful,'' said a steel industry official involved in the White House negotiations.

Administration officials continued negotiations into the night in hopes of coming up with a proposal that would win approval of union leaders by the time the president makes an official announcement, the Post said.

White House aides said on Monday Bush's decision could come as early as Tuesday and that it was possible the president would announce his decision before the Wednesday deadline.

The White House did not immediately return calls seeking comment.

The European Union and other trading partners, including Japan, have threatened to challenge any import restrictions at the World Trade Organization.

In December, the U.S. International Trade Commission sent Bush a mixed bag of recommendations for curbing imports, including tariffs ranging from 8 percent to 40 percent depending on the specific product line.

Bush can accept those recommendations, fashion his own trade remedy or do nothing at all. The last is probably the least likely option because Bush initiated the Section 201 proceeding last summer at the request of the industry.

U.S. steel firms have argued that a uniform tariff is needed to prevent countries from shifting production to those steel products facing the lowest tariffs.

However, U.S. steel-consuming industries and port operators have warned that import restrictions could cost more jobs than they save and raise prices for American consumers.

A senior administration official said last week it was possible import protections could vary by product line with the highest curbs on flat steel.

The official also said a tariff as high as 40 percent may not be necessary to give the domestic industry the breathing space it needs to get back on its feet.

More sophisticated products, including an array of specialized parts made from steel, could be subjected to either quotas or a mix of quota and tariffs, the newspaper quoted officials as saying.

Joe Lockhart, a former spokesman for President Bill Clinton who now represents the Stand Up For Steel coalition, said steel companies and steel workers were alarmed by reports Bush could exempt developing countries from restrictions.

He also urged the administration to impose ``a tariff-based remedy'' on all steel imports, including slab, the most common type of semi-finished steel.

Administration officials have said slab could be treated differently than other steel products because many West Coast steel mills depend on slab imports.

One possibility is a tariff-rate quota, which would let a certain amount of slab come in at reduced duty levels.